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Fix 32-bit zero segment symbol address handling #2

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Fix 32-bit zero segment symbol address handling #2

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8 changes: 5 additions & 3 deletions SymSpec.md
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Original file line number Diff line number Diff line change
Expand Up @@ -47,7 +47,9 @@ else:
The file header as a quite simple structure. Here are the different values you can extract from it (values are all unsigned):
| Size | Explanation |
|:----------:|:----------------------------------------------------------------------------------------|
| 32 bits | This value represents the size of the symbol file, either in bytes or in paragraphs.<br>__This value excludes itself from the count, so add four bytes to this value when comparing to the file size__|
| 16 bits | This value represents the size of the symbol file, either in bytes or in paragraphs.<br>__This value excludes itself and the next two bytes from the count, so add four bytes to this value when comparing to the file size__|
| 8 bits | This value informs us on the nature of the segment zero. We can assume that bit 0 is set if the segment is 32 bits and unset if in 16 bits |
| 8 bits | *Unknown (padding?)* |
| 16 bits | The number of the segment containing the entry point (but no address) |
| 16 bits | This value tells how much symbols you will find in the segment zero (it can just be 0) |
| 16 bits | This value tells in bytes the size of the header __including the 32 bits length__ and __all the content of the zero segment__<br>Basically, it goes from the beginning of the file to the start of the first segment |
Expand All @@ -62,7 +64,7 @@ Then comes the segment zero without any kind of padding. It is a sequence of the
corresponds to the 16 bits value telling how much symbols will be found in segment zero:
| Size | Explanation |
|:----------:|:----------------------------------------------------------------------------------------|
| 16 bits | The address of the symbol. In assembly this should be rather called offset as this values corresponds to n in 0000:nnnnnnnn |
| 16/32 bits | The address of the symbol. In assembly this should be rather called offset as this values corresponds to n in 0000:nnnnnnnn<br>__If the segment is a 32 bits segment, then the size of this value is 32 bits. Else, the size of this value is 16 bits__ |
| 8 bits | Size in bytes of the symbol name that will come after. The size is the exact size, there is no null character |
| 8n bits | The name of the symbol in ASCII (with n = the 8 bits value found above) |

Expand All @@ -78,7 +80,7 @@ communicated by the segment and not trying to continue to read.
| 16 bits | This tells the size in bytes of the segment.<br>__If the symbol file uses bytes and not paragraphs, this value is the address in bytes of the end of the segment__ |
| 16 bits | This tells the segment number n which corresponds in assembly to nnnn:aaaaaaaa where a is an arbitrary value |
| 6*8 bits | *Unknown* |
| 8 bits | This value informs us on the nature of the segment. We can assume that it is only non-null if the segment is 32 bits and null if in 16 bits |
| 8 bits | This value informs us on the nature of the segment. We can assume that bit 0 is set if the segment is 32 bits and unset if in 16 bits |
| 5*8 bits | *Unknown* |
| 8 bits | Size in bytes of the segment name that will come after. The size is the exact size, there is no null character |
| 8n bits | The name of the semgent in ASCII (with n = the 8 bits value found above) |
Expand Down
20 changes: 15 additions & 5 deletions sym2map/SymbolFile.cpp
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Expand Up @@ -50,7 +50,9 @@ bool SymbolFile::ParseSymbolFile() {
uint64_t symFileSize = (symFileEnd - symFileBegin);
symFile.seekg(0, ios::beg);

READ_DATA(symbolFileSize, uint32_t);
READ_DATA(symbolFileSize, uint16_t);
READ_DATA(mapFlags, uint8_t);
symFile.seekg(1, ios::cur); // reserved
READ_DATA(entrySegmentNumber, uint16_t);
READ_DATA(symbolsInHeaderNumber, uint16_t);
READ_DATA(headerTotalSize, uint16_t);
Expand Down Expand Up @@ -88,7 +90,15 @@ bool SymbolFile::ParseSymbolFile() {

SegmentObject segmentZero = SegmentObject();
for (int symbolNumber = 0; symbolNumber < symbolsInHeaderNumber; symbolNumber++) {
READ_DATA(symbolAddress, uint16_t);
uint32_t symbolAddress;
if (mapFlags & 1) {
READ_DATA(addr, uint32_t);
symbolAddress = addr;
}
else {
READ_DATA(addr, uint16_t);
symbolAddress = addr;
}
const string symbolName = ReadLimitedString();
SymbolObject symbol = SymbolObject(symbolAddress, symbolName);
segmentZero.GetEditableSymbolsList().push_back(symbol);
Expand All @@ -112,15 +122,15 @@ bool SymbolFile::ParseSymbolFile() {
/* This was undocumented and has been found when generating a map file with mapsym.exe -t -l and */
/* noticing that the segment in which everything was broken was also the only 32-bit segment */
symFile.seekg(6, ios::cur);
READ_DATA(customSizeMark, uint8_t);
READ_DATA(segmentFlags, uint8_t);
symFile.seekg(5, ios::cur);

const string segmentName = ReadLimitedString();
SegmentObject segment = SegmentObject(segmentNumber, segmentName);
cout << "Segment discovered: " << segmentName << "(" << (customSizeMark ? "32-bits" : "16-bits") << ") - " << symbolsInSegment << " symbols." << endl;
cout << "Segment discovered: " << segmentName << "(" << ((segmentFlags & 1) ? "32-bits" : "16-bits") << ") - " << symbolsInSegment << " symbols." << endl;
for (int symbolNumber = 0; symbolNumber < symbolsInSegment; symbolNumber++) {
uint32_t symbolAddress;
if (customSizeMark) {
if (segmentFlags & 1) {
symFile.read(reinterpret_cast<char*>(&symbolAddress), sizeof(uint32_t));
}
else {
Expand Down